Screening Arrangement

ABSTRACT

A screening panel  10  comprises a peripheral frame  12  consisting of a pair of mutually laterally spaced side members  14, 16 , which are integral with a pair of mutually axially spaced end members  18, 20 . The side members  14, 16  and end members  18, 20  define corners of the panel  22.1, 22.2, 22.3  and  22.4  and the peripheral frame  12  where they meet. A plurality of mutually spaced ribs  15  extend across the periphery of the panel  10  to define a screening surface. The side members and end members are rectangular in cross-section, thereby defining substantially flat upper peripheral surfaces  12.1 , outer peripheral surface  12.2  and lower peripheral surface  12.3  of the peripheral frame  12  and thus also the panel  10 . The panel  10  includes locating recesses  24  provided at or near to the corners  22.1, 22.2, 22.3  and  22.4  of the panel  10 . The panel  10  also has separate securing recesses in the form of semi-circular grooves  30  formed in the lower surface  12.3  of the panel  10 , around the locating recess  24  and concentrically therewith.

THIS INVENTION relates to a screening arrangement. The invention relatesin particular to a screening arrangement for screening particulatematerials such as mineral ores of all types. More particularly, theinvention relates to a screening element; a screening element securingdevice for securing a screening element to a screen support frame; ascreen support frame sub-assembly; a screen support frame; and ascreening arrangement.

According to one aspect of the invention, there is provided a screeningelement securing device for securing a screening element to a screensupport frame, said securing device including

a body portion having a connecting formation for connection to acomplementary formation on a screen support member of a screen supportframe to render the screening element securing device releasablyconnected to the screen support member; and

a locating formation, provided on the body portion, for engagement witha complementary formation on a screening element to locate the screeningelement on the screen support frame.

The body portion may comprise an insert for insertion in an opening inthe screen support member, the connecting formation being provided onthe insert and being for connection to a complementary formation in theopening.

The locating formation may be provided on the insert and comprises alocating protrusion for location in a locating recess of a screeningelement.

The locating protrusion may comprise a shank which extends axially awayfrom the body portion, and a head formed at the free end of the shank.

In one version of this aspect of the invention, the securing device mayinclude a securing formation, separate from the locating formation,which is receivable in a complemental securing formation on thescreening element.

The separate securing formation may comprise a separate securingprotrusion.

The separate securing protrusion may comprise an annular ridge whichstands proud axially of the insert and around the locating protrusion.

The connecting formation may comprise a screw thread for connection to acomplementary connecting formation comprising a complementary screwthread.

In one embodiment of this version, the insert may be monolithic andsubstantially cylindrical, the screw thread being provided on its outersurface, and the insert, shank, head and the annular ridge beingunitary.

In another embodiment of this version of the invention the insert maycomprise a peripheral flange and a skirt fast with the flange, theconnecting formation connectable with a complementary connectingformation on a screen support member being a peripheral radiallyoutwardly facing groove defined in the body portion between the flangeand the skirt, the body portion being resiliently deformable, theannular ridge standing proud axially of the peripheral flange, theinsert defining an axial bore for receiving a pin which pin includes theshank and the head.

In another version of this aspect of the invention, the insert maydefine a locating formation in the form of a secondary opening forengaging the complementary formation on the screening element forlocating and securing the screening element to the screen supportmember, the connecting formation on the insert comprising an externalradially outwardly facing peripheral groove for connection with acomplementary connecting formation in the form of an opening in a screensupport member.

In one embodiment of this version, the insert may comprise a peripheralflange and a skirt fast with the flange, the external peripheral groovebeing defined in the insert between the flange and the skirt, the skirtand the flange defining the secondary opening.

In another embodiment of this version, the insert may define a locatingformation in the form of a secondary opening for engaging thecomplementary formation on the screening element for locating andsecuring the screening element to the screen support member, theconnecting formation on the insert being in the form of an externalscrew thread connectable with a complementary screw thread in an openingin the screen support member.

In this embodiment, the insert may comprise a peripheral flange and askirt fast with the flange, the screw thread being provided on the outersurface of the skirt, and the skirt and the flange together defining thesecondary opening.

The securing device may be of a hard-wearing synthetic plasticsmaterial, such as polyurethane.

According to another aspect of the invention, there is provided ascreening element which has a peripheral frame defining an openingacross which a plurality of mutually spaced ribs extend to define ascreening surface, the peripheral frame having an upper surface on thesame side of the screening element as the screening surface, a lowersurface on its side opposite its upper surface and an outer peripheralsurface interconnecting the upper and lower surfaces, the peripheralframe being provided on its lower surface with locating formations forengagement with complementary locating formations on a screen supportframe to locate the screening element on the screen support framer andthe peripheral frame being provided on its lower surface with separatesecuring formations for engagement with complementary separate securingformations on the screen support frame to secure the screening elementagainst displacement on the screen support frame.

The locating formations may include locating recesses provided in thelower surface of the peripheral frame, respectively for receivinglocating means in the form of locating protrusions on the screen supportframe, for locating adjacent screening elements in position on thescreen support frame.

The separate securing formations may include securing recesses providedin the lower surface of the peripheral frame, respectively for receivingsecuring means in the form of securing protrusions on the screen supportframe, for securing the screening element against displacement on thescreen support frame.

The screening element may be in the form of a screening panel, theperipheral frame comprising a pair of mutually laterally spaced sidemembers which are integral with a pair of mutually longitudinally spacedend members, said side members and end members defining corners of thepanel and peripheral frame where they meet.

The side members and end members of the frame may be rectangular incross-section, thereby defining a substantially flat upper surface, asubstantially flat lower surface and a substantially flat outerperipheral surface for the peripheral frame.

The locating recesses may be provided at or near the corners of thepanel.

The locating recesses may intersect the outer peripheral surface of theperipheral frame, and may be shaped such that when similar locatingrecesses on adjacent panels are brought into register, they and thesimilar locating recesses together define a locating socket into which alocating protrusion on the screen support frame is receivable to locateadjacent panels in position on the support frame.

The separate securing recesses may be formed in the panels near thelocating recesses.

The securing recesses may be endless grooves formed in the lowerperipheral surface of the panel, each extending partly around one of thelocating recesses, there being a securing recess for each locatingrecess.

The grooves may be semi-circular in shape such that, when respectivelybrought into register with similar semi-circular grooves on adjacentpanels, they and the similar grooves together define annular groovesaround their associated locating recesses, for receiving complementaryannular securing protrusions on the support frame, to secure thescreening element against displacement on the support frame in use.

The screening panel may be of resiliently deformable material selectedfrom the group consisting of plastics materials and elastomericmaterials, such that the protrusions fit with interference, or clip,into their associated recesses.

The plastics material may be polyurethane and the elastomeric materialmay be rubber.

According to a further aspect of the invention there is provided ascreen support frame sub-assembly which includes

an elongate screen support member of a screen support frame, the screensupport member having connecting formations; and

a plurality of securing devices releasably connected to the connectingformations of the screen support member;

each securing device including a body portion having a connectingformation for connection to the connecting formations on the screensupport member to render the screening element securing devicereleasably connected to the screen support member; and

a locating formation, provided on the body portion, for engagement witha complementary formation on a screening element to locate the screeningelement on the screen support frame.

According to yet a further aspect of the invention there is provided ascreen support frame which includes a plurality of screen support framesub-assemblies spaced from and parallel to one another and spaced apartfrom one other by a plurality of spacer bars, each sub-assemblyincluding

an elongate screen support member having connecting formations; and

a plurality of securing devices releasably connected to the connectingformations of the screen support member;

such securing device including a body portion having a connectingformation for connection to the connecting formation on the screensupport member to render the screening element securing devicereleasably connected to the screen support frame; and

a locating formation, provided on the body portion, for engagement witha complementary formation on a screening element to locate the screeningelement on the screen support frame.

According to a still further aspect of the invention there is provided ascreening arrangement which includes a screen support frame and aplurality of screening elements secured thereon, each screening elementhaving a peripheral frame defining an opening across which a pluralityof mutually spaced ribs extend to define a screening surface, theperipheral frame having an upper surface on the same side of thescreening element as the screening surface, a lower surface on its sideopposite its upper surface and an outer peripheral surfaceinterconnecting the upper and lower surfaces, the peripheral frame beingprovided on its lower surface with locating formations for engagementwith complementary locating formations on a screen support frame tolocate the screening element on the screen support frame, the screensupport frame including a plurality of screen support framesub-assemblies spaced from and parallel to one another and spaced apartfrom one other by a plurality of spacer bars, each sub-assemblyincluding

an elongate screen support member having connecting formations; and

a plurality of securing devices releasably connected to the connectingformations of the screen support member;

each securing device including

a body portion having a connecting formation for connection to theconnecting formation on the screen support member to render thescreening element securing device releasably connected to the screensupport member; and

a locating formation, provided on the body portion, for engagement witha complementary formation on the screening element to locate thescreening element on the screen support frame.

The peripheral frame of the screening element may be provided on itslower surface with separate securing formations for engagement withcomplementary separate securing formations on the screen support frameto secure the screening element against displacement on the screensupport frame.

The invention will now be described by way of example, with reference tothe accompanying diagrammatic drawings, in which:—

FIG. 1 is an underplan view of a screening panel according to one aspectof the invention;

FIG. 2 is a cross-sectional fragmentary view of a screen support framesub-assembly according to another aspect of the invention, also showing,in fragmentary view, a pair of conventional screening panels (notaccording to the invention) about to be secured to the screen supportframe sub-assembly and in cross-section, one embodiment of a securingdevice according to another aspect of the invention;

FIG. 3 is a three-dimensional view of the securing device of FIG. 2;

FIG. 4 is a cross-sectional fragmentary view of a screen support framesub-assembly according to the invention, also showing, in fragmentaryview, a pair of conventional screening panels (not according to theinvention) about to be secured to the screen support frame component,and in cross-section, another embodiment of a securing device accordingto another aspect of the invention;

FIG. 5 shows a three-dimensional view of the securing device of FIG. 4;

FIG. 6 shows a cross-sectional exploded view of a screen support framesub-assembly and in fragmentary view a pair of screening panelsaccording to the invention with locating and securing formations tolocate and secure the screening panels to the screen support framecomponent sub-assembly, and in cross-section, another embodiment of asecuring device according to another aspect of the invention;

FIG. 7 shows a cross-sectional fragmentary exploded view, similar toFIG. 6, of another embodiment of the invention;

FIG. 8 shows a fragmentary cross-sectional view of the version of theembodiment of FIG. 7 once the locating and securing formations on thescreening elements have engaged complementary formations on a securingdevice of the screen support frame sub-assembly;

FIG. 9 shows a fragmentary cross-sectional view of screening panels,another embodiment of a screen support frame sub-assembly and anotherembodiment of a securing device according to the invention;

FIG. 10 shows a fragmentary partly cross-sectional side view of anelongate screen support member of a screen support frame sub-assemblyhaving tubular members affixed thereto and securing devices according toanother embodiment of the invention connected to the tubular members;

FIG. 11 shows a fragmentary side view of a screen support framesub-assembly according to the invention;

FIG. 12 shows a top plan view of the sub-assembly of FIG. 11; and

FIG. 13 shows a fragmentary top plan view of a screen support frame andscreening arrangement in accordance with another aspect of theinvention.

In FIG. 1 of the drawings, reference numeral 10 generally indicates ascreening panel in accordance with one aspect of the invention. Thescreening panel comprises a peripheral frame 12 consisting of a pair ofmutually laterally spaced side members 14, 16, which are integral with apair of mutually axially spaced end members 18, 20. The side members 14,16 and end members 18, 20 define corners of the panel 22.1, 22.2, 22.3and 22.4 and the peripheral frame 12 where they meet. A plurality ofmutually spaced ribs 15 extend across the periphery of the panel 10 todefine a screening surface (not shown). The side members and end membersare rectangular in cross-section, thereby defining substantially flatupper peripheral surfaces 12.1 (FIGS. 6, 7 and 8), outer peripheralsurface 12.2 and lower peripheral surface 12.3 of the peripheral frame12 and thus also the panel 10. The panel 10 includes locating recesses24 provided at or near to the corners 22.1, 22.2, 22.3 and 22.4 of thepanel 10. The locating recesses 24 are formed in the lower peripheralsurface 12.3 and intersect the outer peripheral surface 12.2 of thepanel 10 as can more clearly be seen in FIGS. 6, 7, 8 and 9 of thedrawings. As may also more clearly be seen from FIGS. 6, 7, 8 and 9 ofthe drawings, when similar locating recesses 24 on adjacent panels 10are brought into register with one another, they together define alocating socket 26 into which a protrusion or spigot 28, 29, 31, 33which is complementarily shaped, can be received to locate adjacentpanels 10 in position on a support frame 80 (see FIG. 13).

The panel 10 also has separate securing recesses in the form ofsemi-circular grooves 30 formed in the lower surface 12.3 of the panel10, around the locating recess 24 and concentrically therewith. As canbe seen from FIGS. 8 and 9, when brought into register with a similarsemi-circular groove 30 on an adjacent panel 10, the grooves 30 togetherdefine an annular groove to receive a complemental securing formation inthe form of an annular ridge 32 on a screen support frame sub-assembly36.

The invention extends to a screen support frame sub-assembly generallyindicated by reference numeral 36. In the embodiment shown in FIGS. 2,4, 6, 7, 8 and 10, the elongate screen support member of thesub-assembly 36 is an elongate bar 38 which has a rectangularcross-sectional profile of oblong shape, and cut-outs 39 into whichtubular elements 40 can fit and are affixed to the bar by welding suchthat the longitudinal axis of the tubular element 40 extends in thedirection of the longitudinal axis of the oblong cross-sectional profileof the bar 40. Each tubular element 40 defines an opening in the screensupport member 38 which opening is a primary socket 42 into which asecuring device, generally indicated by reference numeral 44 in FIGS. 2and 3, 46 in FIGS. 4 and 5, 48 in FIG. 6, 49 in FIGS. 7 and 8, and 51 inFIG. 10, is releasably connectable as will be explained below.

It is to be understood that the versions of the securing devices andsub-assemblies of the invention shown in FIGS. 2, 3, 4 and 5 areintended for use with a screening panel 11 which is a known screeningpanel, and not a screening panel 10 in accordance with the invention.

The securing devices 44, 46 shown in FIGS. 2 to 5, are configured toengage locating formations in the form of protrusions 13 on screeningpanels 11, to locate and secure the screening panels 11 to a screensupport frame sub-assembly 36, in the manner described below.

With reference to FIGS. 2, 4 and 6 to 8, a plurality of tubular elements40 are affixed to the elongate bar 38, the tubular elements 40 beingspaced from each other by distances complementary to the spacing betweenlocating recesses 24 and grooves 30 in panels 10 according to theinvention, or protrusions 13 in known panels 11, by means of which thescreening panels 10, 11 are located and/or secured to the elongate bar38 and thereby to a support frame of similar kind to the support frame80 (FIG. 13). The width of the elongate bar 38 is smaller than thecross-sectional dimension of the primary socket 42.

In the version of this embodiment of the invention shown in FIGS. 2 and3 of the drawings, the connecting formation in the primary socket 42 isa ridge or lip 52 extending peripherally around the upper open end 41 ofthe tubular member 40. In this embodiment of the invention, the securingdevice 44 is of a hard-wearing synthetic plastics material such aspolyurethane having a Shore hardness of 95 to 99 Shore A. The device 44includes an insert 45 which comprises a peripheral flange 54 and astepped, downwardly depending skirt 56 fast with the flange 54, theflange 54 and skirt 56 defining a secondary opening in the form of asecondary socket 59. An external, radially outwardly facing peripheralgroove 58 is defined between the flange 54 and the skirt 56 such that,when the skirt fits with interference into the primary socket 42 definedby the tubular element 40, the peripheral groove 58 engages the lip 52to retain the device 44 within the primary socket 42, thereby to connectthe device 44 to the bar 38.

Instead, in another version, shown in FIGS. 4 and 5 of the drawings, theconnecting formation in the primary socket 42 is a screw thread 60. Thesecuring device 46 is then also of hard-wearing synthetic plasticsmaterial and includes an insert 61 which comprises a flange 62 extendingperipherally around the open upper end of the insert, and a downwardlydepending skirt 64 fast with the flange 62, the flange 62 and the skirt64 defining a secondary opening in the form of a secondary socket 63. Anexternal screw-thread 66 which is complementary to the screw-thread 60is provided on the outer surface of the skirt 64. The device 46 can bescrewed into the socket 42 by means of a key (not shown) which hasprongs to fit into key holes 68 provided in the flange 62. In theseembodiments of the invention, as shown in FIGS. 2 and 4 of the drawings,the screening panels 11 are provided with protrusions 13 on theirundersurfaces which, when adjacent panels are brought into register withone another will fit into the secondary sockets 59 and 63 formed in thedevices 44, 46, and securing pins 17 are then knocked into complementalbores 19 which are formed when the panels are brought into register withone another, to secure the panels 11 to the elongate bar 38.

It is an advantage of the screen support frame sub-assemblies and thedevices 44, 46 according to this aspect of the invention that thedevices 44, 46 can easily be replaced when they become worn in use as aresult of the stresses placed on the screening panels being transmittedvia the protrusions 13 to the inserts 44, 46.

In another version of this aspect of the invention, shown in FIGS. 6 to10 of the drawings, the devices 48, 49, 50 and 51 include locatingprotrusions or spigots 28, 29, 31 and 33 which extend axially from thedevices. It is to be understood that the versions of the aspect of theinvention shown in FIGS. 6 to 10 of the drawings are intended for usewith screening panels 10 according to the invention.

In the embodiment shown in FIG. 6 of the drawings, the device 48includes an insert which comprises a monolithic cylindrical body portion48.1 provided with a screw-thread 48.2 on its outer surface, which iscomplementary to a screw-thread 42.1 provided on the inner surface ofthe primary socket 42 formed by the tubular element 40. The insert 48also has an annular ridge 70 which has an overhanging radially inwardlydirected lip 70.1, which form separate securing formations standingproud of the upper surface 48.3 of the insert 48, and which arereceivable with interference within complementary semi-circular recesses72 provided in panels 10 according to the invention, which semi-circularrecesses 72, when the panels are brought into register, form annularrecesses. The protrusion or spigot 28 extends axially away from the body48.1 of the insert 48 and comprises a shank member 28.1 and a head 28.2,which fit with interference into the locating socket 26 formed whenadjacent panels 10 according to the invention are brought into registerto be secured to an elongate bar 38.

In the embodiment shown in FIGS. 7 and 8 of the drawings, the device 49is similar to the device 48 of FIG. 6 of the drawings, except that theannular ridge 32 has a rounded upper surface 32.1 which fits withinterference into complementary semi-circular securing recess 30 in thepanels 10 according to the invention. Furthermore, the protrusion orspigot 29 on the insert 49 comprises a shank 29.1 similar to the shank28.1 of the insert 48, but a more rounded head 29.2 at the end of theshank 28.1.

In the embodiment shown in FIG. 10 of the drawings, the tubular elements40 are recessed into the cut outs 39 of the elongate bar 38. The device51 is similar to the device 48 of FIG. 6 of the drawings, except thatthe annular ridge 82 has a sharper upper surface 82.1 which will fitwith interference into complementary semi-circular recess in the panels10 according to the invention. The device 51 also includes an insertwhich comprises a monolithic cylindrical body portion 51.1 provided withan external screw thread 51.2 which is complementary to the screw thread42.1 provided on the inner surface of the primary socket 42 formed bythe tubular element 40. The locating protrusion 33 comprises a shankmember 33.1 and a head 33.2 similar to those of the devices 48 of FIG.6. It is also to be noted that in the embodiment of FIG. 10, when thedevice 51 is screwed into place into the tubular member 40, the uppersurface 51.3 of the device is flush with the upper surface 38.1 of theelongate bar 38.

In the embodiments of FIGS. 6, 7, 8 and 10, the devices shown areunitary.

Instead, in the embodiment shown in FIG. 9 of the drawings the securingdevice 50 comprises an insert 50.1 which comprises a peripheral flange50.2 and a resiliently deformable skirt 50.3 fast with the flange 50.2,a peripheral radially outwardly facing groove 50.4 being defined in thebody portion between the flange 50.2 and the skirt 50.3, and an annularridge which stands proud axially of the peripheral flange 50.2. Theinsert 50.1 defines an axial bore 50.6 for receiving a separate pin 90,which pin 90 incorporates a shank 90.1 and a head 90.2. In thisembodiment, an elongate screen support member can be in the form of anelongate channel iron section 100 having openings 102 formed therein oran elongate bar 38 having openings in the form of a primary socket 42 asshown in FIG. 2, at desired intervals as described before. When thesecuring device 50 is to be used on existing screen support frames whichcomprise said elongate bars 38 or channel irons 100, the resilientlydeformable portion 50.3 can be urged into the openings 42 in the tubularmembers 40, or openings 102 in the channel iron, as the case may be.Thereafter, the pin 90 which is formed with a bulge 91 is urged into theaxial bore, the bulge 91 expanding the skirt 50.3 and the peripherallyradially outwardly facing groove 50.4 engaging with the edges of theopening 102, or the lip 52, as the case may be, to connect the securingdevice 50 to the channel section 100 or bar 38 as the case may be. Thepanels 10 according to the invention can then be located and secured onthe channel sections 100 or bars 38 in the manner similar to thatdescribed with reference to FIGS. 6 to 8 above. The particular advantageof this embodiment of the securing device and screening panel of theinvention is that they can be used on existing screen support frameswhich are made of channel iron sections 100, or bars 38 having tubularmembers 40 as shown in FIG. 2 affixed thereto.

A screen support frame sub-assembly 36 as shown in FIGS. 11 and 12 ofthe drawings comprises an elongate bar 38 having cut outs 39 therein,and a plurality of tubular elements 40 affixed thereto, the tubularelements 40 being spaced from each other by distances complementary tothe spacing between locating recesses 24 and grooves 30 in the panels 10according to the invention.

A screen support frame 80 as shown in FIG. 13 of the drawings comprisesa plurality of elongate bars 38 as described, which are spaced from andparallel to each other and spaced apart from each other by spacer bars78, thereby to form a grid-like structure on which screening panels 10,101 can be fitted as described, to provide a screening arrangement.

It is an advantage of the embodiment of the invention as illustrated inFIGS. 6 to 10 of the drawings that the devices 48, 49, 50 and 51 have,in combination, locating formations in the form of the protrusions orspigots 28, 29, 31 and 33 as well as separate securing formations in theform of the annular ridges 70, 82, 32, and 50.5 respectively, whichengage complementary formations 30 and 72 on the screening panels 10 inaccordance with the invention. The locating protrusions locate thepanels in place on the elongate support bars 38, and the annular ridgessecure the panels in place against transverse movement on the elongatesupport bar 38, or the channel sections 100 as the case may be, in use.In conventional screening panels known to the Applicant, in the absenceof a combination of the protrusions 28, 29 and the annular ridges 70, 32and complemental recesses 72, 30 in the panels 10, the panels 10 tend tobecome dislodged and move transversely across a screen in use. It is afurther advantage that the screening area of a panel which is availableis increased by virtue of the fact that only half of the periphery of apanel 10 rests on the elongate support bar 38. It is yet a furtheradvantage that the securing devices 48 and 50 also being of hardwearingsynthetic plastics material, ensures easier mating and disconnection ofthe panels 10 from the protrusions 28 and annular ridges 32 in use whenrequired to do so, either to replace the panels 10, the securing devices48, 50, or both.

1. A screening element securing device for securing a screening elementto a screen support frame, said securing device including a body portionhaving a connecting formation for connection to a complementaryformation on a screen support member of a screen support frame to renderthe screening element securing device releasably connected to the screensupport member; and a locating formation, provided on the body portion,for engagement with a complementary formation on a screening element tolocate the screening element on the screen support frame.
 2. A securingdevice as claimed in claim 1 wherein the body portion comprises aninsert for insertion in an opening in the screen support member, theconnecting formation being provided on the insert and being forconnection to a complementary formation in the opening.
 3. A securingdevice as claimed in claim 2 wherein the locating formation is providedon the insert and comprises a locating protrusion for location in alocating recess of a screening element.
 4. A securing device as claimedin claim 3 wherein the locating protrusion comprises a shank whichextends axially away from the body portion, and a head formed at thefree end of the shank.
 5. A securing device as claimed in claim 3 orclaim 4 which includes a securing formation, separate from the locatingformation, which is receivable in a complemental securing formation onthe screening element.
 6. A securing device as claimed in claim 5 wherethe separate securing formation comprises a separate securingprotrusion.
 7. A securing device as claimed in claim 6 wherein theseparate securing protrusion comprises an annular ridge which standsproud axially of the insert and around the locating protrusion.
 8. Asecuring device as claimed in claim 7 wherein the connecting formationcomprises a screw thread for connection to a complementary connectingformation comprising a complementary screw thread.
 9. A securing deviceas claimed in claim 8 wherein the insert is substantially cylindrical,the screw thread being provided on its outer surface, and the insert,shank, head and the annular ridge being unitary.
 10. A securing deviceas claimed in claim 7 wherein the insert comprises a peripheral flangeand a skirt fast with the flange, the connecting formation connectablewith a complementary connecting formation on a screen support memberbeing a peripheral radially outwardly facing groove defined in the bodyportion between the flange and the skirt, the body portion beingresiliently deformable, the annular ridge standing proud axially of theperipheral flange, the insert defining an axial bore for receiving a pinwhich pin includes the shank and the head.
 11. A securing device asclaimed in claim 2 wherein the insert defines a locating formation inthe form of a secondary opening for engaging the complementary formationon the screening element for locating and securing the screening elementto the screen support member, the connecting formation on the insertcomprising an external radially outwardly facing peripheral groove forconnection with a complementary connecting formation in the form of anopening in a screen support member.
 12. A securing device as claimed inclaim 11 wherein the insert comprises a peripheral flange and a skirtfast with the flange, the external peripheral groove being defined inthe insert between the flange and the skirt, the skirt and the flangedefining the secondary opening.
 13. A securing device as claimed inclaim 2 wherein the insert defines a locating formation in the form of asecondary opening for engaging the complementary formation on thescreening element for locating and securing the screening element to thescreen support member, the connecting formation on the insert being inthe form of an external screw thread connectable with a complementaryscrew thread in an opening in the screen support member.
 14. A securingdevice as claimed in claim 13 wherein the insert comprises a peripheralflange and a skirt fast with the flange, the screw thread being providedon the outer surface of the skirt, and the skirt and the flange togetherdefining the secondary opening.
 15. A securing device as claimed inclaim 1, which is of a hard-wearing synthetic plastics material.
 16. Ascreening element which has a peripheral frame defining an openingacross which a plurality of mutually spaced ribs extend to define ascreening surface, the peripheral frame having an upper surface on thesame side of the screening element as the screening surface, a lowersurface on its side opposite its upper surface and an outer peripheralsurface interconnecting the upper and lower surfaces, the peripheralframe being provided on its lower surface with locating formations forengagement with complementary locating formations on a screen supportframe to locate the screening element on the screen support frame, andthe peripheral frame being provided on its lower surface with separatesecuring formations for engagement with complementary separate securingformations on the screen support frame to secure the screening elementagainst displacement on the screen support frame.
 17. A screeningelement as claimed in claim 16 wherein the locating formations includelocating recesses provided in the lower surface of the peripheral frame,respectively for receiving locating means in the form of locatingprotrusions on the screen support frame, for locating adjacent screeningelements in position on the screen support frame.
 18. A screeningelement as claimed in claim 16 wherein the separate securing formationsinclude securing recesses provided in the lower surface of theperipheral frame, respectively for receiving securing means in the formof securing protrusions on the screen support frame, for securing thescreening element against displacement on the screen support frame. 19.A screening element as claimed in claim 17 or claim 18, which is in theform of a screening panel, the peripheral frame comprising a pair ofmutually laterally spaced side members which are integral with a pair ofmutually longitudinally spaced end members, said side members and endmembers defining corners of the panel and peripheral frame where theymeet.
 20. A screening panel as claimed in claim 19 wherein the sidemembers and end members of the frame are rectangular in cross-section,thereby defining a substantially flat upper surface, a substantiallyflat lower surface and a substantially flat outer peripheral surface forthe peripheral frame.
 21. A screening panel as claimed in claim 20wherein the locating recesses are provided at or near the corners of thepanel.
 22. A screening panel as claimed in claim 21 wherein the locatingrecesses intersect the outer peripheral surface of the peripheral frame,and are shaped such that when similar locating recesses on adjacentpanels are brought into register they and the similar locating recessestogether define a locating socket into which a locating protrusion onthe screen support frame is receivable to locate adjacent panels inposition on the support frame.
 23. A screening panel as claimed in claim22 wherein the separate securing recesses are formed in the panels nearthe locating recesses.
 24. A screening panel as claimed in claim 23wherein the securing recesses are endless grooves formed in the lowerperipheral surface of the panel, each extending partly around one of thelocating recesses, there being a securing recess for each locatingrecess.
 25. A screening panel as claimed in claim 24 where in thegrooves are semi-circular in shape such that when respectively broughtinto register with similar semi-circular grooves on adjacent panels,they and the similar grooves together define annular grooves aroundtheir associated locating recesses, for receiving complementary annularsecuring protrusions on the support frame.
 26. A screening panel asclaimed in claim 16, which is of resiliently deformable materialselected from the group consisting of plastics materials and elastomericmaterials.
 27. A screening panel as claimed in claim 26 wherein theplastics material is polyurethane and the elastomeric material isrubber.
 28. A screen support frame sub-assembly which includes anelongate screen support member of a screen support frame, the screensupport member having connecting formations; and a plurality of securingdevices releasably connected to the connecting formations of the screensupport member; each securing device including a body portion having aconnecting formation for connection to the connecting formations on thescreen support member to render the screening element securing devicereleasably connected to the screen support member; and a locatingformation, provided on the body portion, for engagement with acomplementary formation on a screening element to locate the screeningelement on the screen support frame.
 29. A screen support frame whichincludes a plurality of screen support frame sub-assemblies spaced fromand parallel to one another and spaced apart from one other by aplurality of spacer bars, each sub-assembly including an elongate screensupport member having connecting formations; and a plurality of securingdevices releasably connected to the connecting formations of the screensupport member; such securing device including a body portion having aconnecting formation for connection to the connecting formation on thescreen support member to render the screening element securing devicereleasably connected to the screen support frame; and a locatingformation, provided on the body portion, for engagement with acomplementary formation on a screening element to locate the screeningelement on the screen support frame.
 30. A screening arrangement whichincludes a screen support frame and a plurality of screening elementssecured thereon, each screening element having a peripheral framedefining an opening across which a plurality of mutually spaced ribsextend to define a screening surface, the peripheral frame having anupper surface on the same side of the screening element as the screeningsurface, a lower surface on its side opposite its upper surface and anouter peripheral surface interconnecting the upper and lower surfaces,the peripheral frame being provided on its lower surface with locatingformations for engagement with complementary locating formations on ascreen support frame to locate the screening element on the screensupport frame, the screen support frame including a plurality of screensupport frame sub-assemblies spaced from and parallel to one another andspaced apart from one other by a plurality of spacer bars, eachsub-assembly including an elongate screen support member havingconnecting formations; and a plurality of securing devices releasablyconnected to the connecting formations of the screen support member;each securing device including a body portion having a connectingformation for connection to the connecting formation on the screensupport member to render the screening element securing devicereleasably connected to the screen support member; and a locatingformation, provided on the body portion, for engagement with acomplementary formation on the screening element to locate the screeningelement on the screen support frame.
 31. A screening arrangement asclaimed in claim 30 wherein the peripheral frame of the screeningelement is provided on its lower surface with separate securingformations for engagement with complementary separate securingformations on the screen support frame to secure the screening elementagainst displacement on the screen support frame.